Various types of vehicles, such as automobiles, trucks, boats, and the like, utilize rearview mirrors mounted externally, usually on the driver's door and sometimes on the passenger's door as well. In order to use the mirror, the driver must look through the side window adjacent the mirror. However, in adverse weather conditions, such as rain or snow, the driver's view through the externally mounted rearview mirror may be obstructed, either because of moisture on the mirror itself, or on the window adjacent the mirror through which the driver must look.